[unreadable] The goal of the research is to develop a method of optical pharmacokinetics (OP), and demonstrate that such technology can be used to determine drug concentrations at different depths within tissues. The drug concentrations in tissue vary through time, and the distribution of the drug also varies at different tissue locations and tissue layers. A non-invasive method for studying pharmacokinetics will have several applications for improving the dosimetry of photodynamic therapy (PDT). PDT is a promising technique for producing localized necrosis of tissue with light after prior administration of a photosensitizing drug. The effect of PDT depends on the tissue concentration of drug and the light absorbed by the drug at different tissue locations exceeding a threshold. It is difficult to predict the light dose required for a PDT effect at each point in the target tissue. Another application for the OP system will include detecting changes in capillary permeability caused by anti-angiogenic therapy. [unreadable] [unreadable] [unreadable]